1. Field of the Invention
This invention relates generally to the field of drywall construction and more particularly to adjustable prefabricated interior 3-way corners for completion of drywall installation in construction.
2. Description of the Related Art
The use of gypsum drywall board in modern construction is well known. Manufactured drywall sheets are nailed to studs to form interior walls and ceilings. Before these sheets can be painted or textured, the joints must be taped and sealed with joint sealing compound (drywall mud).
In some special cases, metal beads or seams are used, as well as metal nailed corners. U.S. Pat. No. 5,086,598 is an example of extruded plastic strips and corners which are nailed. In U.S. Pat. No. 5,086,598 a system of raised members is nailed into place. This is mainly used for exterior corners. However, the bulk of finished drywall work requires taping with paper and the application of drywall mud. All finished surfaces and corners must end up completely smooth and flush. Raised surfaces or bumps, as well as imperfections, are not allowed. Drywall workers spend considerable work time to accomplish this. The dry taped, mudded surface is finished and becomes the final surface that receives paint or texture.
A professional drywall worker commonly tapes (strings) all interior seams with a tool known in the trade as a "bazooka". The bazooka dispenses both drywall tape and mud at the same time. Stringing straight seams in the center of walls and ceilings with a bazooka is relatively easy; however, stringing joints where walls or walls and ceilings come together is considerably more difficult. The most difficult, time-consuming, and frustrating task is stringing the pointed, 3-way corners where two walls and a ceiling come together. It is to this type of corner that the present invention relates and finds great utility.
To string an interior wall-ceiling seam with two 3-way corners, the worker starts the tape at one pointed corner of the room and works along the ceiling toward the other pointed corner. As the tape and mud strings out of the bazooka, the tape has a tendency to slip in the direction of the pull (away from the first corner). Thus, even though the tape was started in the first corner, by the time the worker reaches the second corner, the tape has slipped away from the first corner by up to an inch in some cases. As the worker approaches the second corner, there is no way to pull the bazooka completely into the second corner. This forces the worker to cut the tape away from the corner guessing at the correct length by experience. The tape is usually either cut short or long in the second corner, even by experienced drywall workers. The slippage of the tape away from the first corner, and the over or under cut of the tape in the second corner, make it difficult to achieve perfectly finished taped 3-way corners, and requires recutting and patching by hand.
Once the tape is strung, the worker must "roll" and "glaze" to pre-finish the taped seams and angles (corners) to press the tape into place and remove excess mud. A roller is first rolled along all tapes to firmly seat the tape into position. Then, a glazer is run along the tape to leave the mud as a thin uniform film. When the worker reaches the 3-way corner, neither the roller or glazer will fit into the corner. In addition, the worker finds that the tape usually is too long or short in the corner for the reasons already mentioned. The worker must first fix the tape length, and then attempt to glaze by hand using a wide knife blade. This step in the corners is very slow and extremely frustrating. The result must be a perfectly clean and glazed 3-way corner, something difficult to achieve.
Once the tape and mud has dried (usually the next day), the professional taper will coat the angles with topping mud using a glazer and angle box. Again, as the worker coats the tape, the mud will accumulate into the 3-way corners. This mud needs to be "starred" or pulled in different directions with a 4 to 6 inch knife. Again the problems of producing a perfect 3-way finished corner arise. This time they are more acute since this is the last step in the process, and the result must be perfect. Depending on the finish of the walls (texture, orange peel, smooth, etc.), this process may need to be repeated a few times. With as many as seventy 3-way corners in a typical 2000 sq. foot house, the amount of hours spent processing 3-way corners becomes extremely large.
While the prior art is replete with devices, corner beads, re-enforcement members, etc. to form 2-way joints, there is virtually no notice of any method or apparatus to ease the work and frustration of un-beaded, un-nailed, flat 3-way corners. Since these corners are prevalent in almost all residential construction and much commercial construction, what is badly needed in the art is an adjustable apparatus that allows easy application of tape and mud to 3-way corners of any angles with the bazooka; easy rolling and glazing into the corners; and easy application of topping mud and finishing these same corners. The savings in work hours would be immense. Since the frustration of finishing so many corners would be removed, the professional worker could spend more time on more critical parts of the job and save time and money by completing the job faster with higher quality.